Heavy metals are highly persistent pollutants in the environment.These metals are used in various industries from which effluents are consequently discharged into the environment. Metals usually accumulate at higher concentration in the soil than in water because it is diluted in soil than in water easily. Soils are composed of minerals which can naturally contain high concentrations of metals. Capacity of soils will allow metals to attach to soil particles in response to ionic attractions and accumulate. Several biotic and abiotic factors can influence the specification and toxicity of metals in the soil. These factors interact to influence metal speciation, bioavailability and overall toxicity. Thus, it must be emphasized that determination of the total concentration of a metal in a soil is not enough to predict toxicity in biological systems.Most of the research on metal bioavailability has been done in soil because of understanding the rate of metal in soil and sediment and also used to determine the effect of metals on the biota, metal leaching to ground water and metal transfer up the food chain.
Humans are primarily exposed to various types of Pollutants and one such pollutant is Toluene. It is moderately toxic when ingested or inhaled and slightly hazardous when absorbed through skin. Toluene can enter human body from the air, water or soil. When toluene is inhaled, it is directly taken into the blood from the lungs. When toluene is ingested, it is absorbed from the GI tract into the bloodstream. Small amount of toluene accumulates in fat tissue with daily exposure and majority of toluene is removed from the body within a day. Toluene leaves the body unchanged during respiration and excretion or it is converted into a less harmful chemical such as hippuric acid.Bioremediation is the best practice of using living organisms to detoxify the polluted environment. There are three different types of bioremediation namely (a) Microbial bioremediation, (b) Phytoremediation and (c) Mycoremediation. The process of using microbes to degrade environmental contaminants to non harmful or less harmful products is termed as microbial biodegradation which can occur aerobically or anaerobically.Aerobic degradation occurs when the pollutant is oxidised using oxygen, nitrogen, iron, sulphate and manganese by the microbes and the pollutant acts as electron donor. Anaerobic degradation occurs when the pollutant is reduced by the microbes. The oxidative microbes degrade toluene via hydroxylation of the aromatic ring to a mixture of catechols and cresols.The present research work is a Comparative study of bacteria isolated from polluted environments that are capable of degrading toluene.
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